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## Septran (Co-trimoxazole)
### Overview
Septran is a combination antibiotic containing sulfamethoxazole and trimethoprim. It is a synthetic antibacterial agent.
### Primary Indications
* Treatment of urinary tract infections (UTIs) due to susceptible organisms.
* Treatment of acute exacerbations of chronic bronchitis.
* Treatment of Pneumocystis jirovecii pneumonia (PCP).
* Prophylaxis and treatment of toxoplasmosis.
### Adult Dosing
* **Urinary Tract Infections:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 12 hours for 3 to 7 days (for acute cystitis) or 10 to 14 days (for acute pyelonephritis).
* **Acute Exacerbations of Chronic Bronchitis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 12 hours for 7 days.
* **Pneumocystis jirovecii Pneumonia (PCP) - Treatment:** 15 to 20 mg/kg trimethoprim and 75 to 100 mg/kg sulfamethoxazole per day, divided into 3 or 4 doses, for 14 to 21 days.
* **Pneumocystis jirovecii Pneumonia (PCP) - Prophylaxis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) daily, or 3 times a week on alternate days.
### Pediatric Dosing
Dosing is based on trimethoprim component.
* **Urinary Tract Infections and Shigellosis:** 8 mg/kg trimethoprim and 40 mg/kg sulfamethoxazole per day, divided into 2 doses, administered every 12 hours for 7 to 10 days for UTIs and 5 days for shigellosis.
* **Pneumocystis jirovecii Pneumonia (PCP) - Treatment:** 15 to 20 mg/kg trimethoprim and 75 to 100 mg/kg sulfamethoxazole per day, divided into 3 or 4 doses, for 14 to 21 days.
* **Pneumocystis jirovecii Pneumonia (PCP) - Prophylaxis:** 5 mg/kg trimethoprim and 25 mg/kg sulfamethoxazole per day, divided into 2 doses, administered every 12 hours for 3 days a week on consecutive days.
### Dose Adjustments
* **Renal Impairment:**
* CrCl > 30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Half the usual dose.
* CrCl < 15 mL/min: Contraindicated.
### Contraindications
* Known hypersensitivity to trimethoprim or sulfonamides.
* Documented megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age (risk of kernicterus).
* Severe renal insufficiency (CrCl < 15 mL/min).
* Severe hepatic insufficiency.
### Adverse Effects
* **Common:** Nausea, vomiting, rash (including Stevens-Johnson syndrome and toxic epidermal necrolysis), urticaria, pruritus, eosinophilia.
* **Serious:** Hematologic abnormalities (leukopenia, thrombocytopenia, hemolytic anemia, aplastic anemia, megaloblastic anemia), hyperkalemia, liver dysfunction, crystalluria, photosensitivity, pseudomembranous colitis, exacerbation of asthma.
### Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely.
* **Methotrexate:** Increased risk of methotrexate toxicity. Avoid concurrent use or monitor methotrexate levels.
* **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia.
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Cyclosporine:** Increased cyclosporine levels, particularly in renal transplant patients.
* **Oral contraceptives:** May reduce efficacy.
### Monitoring
* Complete blood counts (CBC) with differential and platelet count should be performed periodically, especially in patients on prolonged therapy or with impaired renal function.
* Renal function.
* Liver function tests.
* Electrolytes, particularly potassium.
* Signs of hypersensitivity reactions and skin rashes.
### Clinical Pearls
* Encourage adequate fluid intake to prevent crystalluria.
* Sulfonamides can displace bilirubin from albumin; use with caution in jaundiced infants.
* Monitor for signs of bone marrow suppression.
* Co-trimoxazole is a preferred agent for PCP prophylaxis and treatment.
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*This information is intended for clinical pharmacists and healthcare professionals. Always consult the most current prescribing information and local protocols.*
